Project Summary Emergency departments (EDs) are an ideal venue to conduct screening for both HIV and HCV, given the high prevalence of HIV and HCV risk-taking behaviors among ED patients (e.g., sexual risk and drug use, particularly injection-drug use during the current opioid epidemic in the US); the known feasibility and acceptability of HIV and HCV screening in this setting; the proven yield of identifying those with undiagnosed infections in the ED; and the ability to link those with infections to subsequent care after the ED visit. Screening for both infections in EDs is preferable due to: (1) the shared overlap of some risk behaviors for HIV and HCV acquisition (e.g., drug use), (2) the relatively high co-occurrence of these infections in some populations, (3) the more complex medical needs and worse sequelae for those co-infected, and (4) efficiency. Despite the strong rationale for ED HIV/HCV screening, best practices on how to conduct screening so to maximize patient screening uptake have yet to be identified. Two important unanswered questions in particular limit our understanding and impede screening efforts: (1) How can we convince patients who decline HIV/HCV screening to be tested? and (2) Who should conduct screening to maximize screening uptake? In this current R34 project, we will conduct crucial preparatory work for a subsequent R01 randomized, controlled trial (RCT) to address these two unanswered questions on ED HIV/HCV screening. For Aim 1, we will further develop and refine a persuasive health communication intervention designed to convince ED patients who decline opt-out rapid HIV/HCV screening to be tested. We will present our draft persuasive health communication intervention to: (a) those who will deliver it (i.e., ED medical staff and HIV/HCV counselors) and to (b) the intended recipients (i.e., adult ED patients who decline opt-out rapid HIV/HCV screening). We will improve the intervention in an iterative fashion based on these stakeholders' perspectives and suggestions regarding its persuasiveness, acceptability, and respect for autonomy. For Aim 2, we will conduct a R34 pilot RCT to assess the feasibility and acceptability of the persuasive health communication intervention and estimate its initial efficacy in increasing HIV/HCV screening uptake among adult ED patients who decline opt-out HIV/HCV screening. As a primary measure of the intervention's initial efficacy in increasing ED patient uptake of HIV/HCV testing, we will compare the intervention to a brief video based on Centers for Disease Control and Prevention (CDC) brochures that provides information to encourage HIV and HCV testing. As a secondary measure of the intervention's initial efficacy, we will compare ED HIV/HCV testing uptake when it is delivered by HIV/HCV counselors vs. ED medical staff. Our working hypotheses are that the intervention will be more efficacious than the video, and more efficacious when delivered by ED medical staff. This R34 pilot study will confirm the feasibility and acceptability of the intervention, and provide effect sizes estimates for the subsequent R01 RCT.